Note: Descriptions are shown in the official language in which they were submitted.
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The field of the invention is pneumatic timing
devices, and more particularly, those devices used in
timing relays to provide a time delay between the opera-
tion of a relay electromagnet and the actuation of some
relay switch contacts. Timing relays are used in circuits
for controlling industrial machines and processes of
many kinds, particularly those machines and processes
that are driven by one or more electrical motorsO
Pneumatic timers with needle-type valves are
disclosed in Haydu et al, U.S. Patent No. 3,249,716,
issued December 26, 1963, and in Selas, U.S. Patent
No. 4,303,147, issued December 1, 1981, and assigned
to the assignee of the present invention. This last
patent is directed to an adjustment mechanism for
controlling the axial position of a valve needle. The
needle extends from a valve chamber into a passageway
that opens into the interior of a bellows. The valve
needle controls the rate of air flow into the bellows,
thereby controlling its expansion.
Besides having a mechanical adjustment that is
easily and conveniently operated, a pneumatic timer
should permit an operator to easily locate a particular
time setting. The scale on the typical timer provides
only an approximate setting. The scale is used to make
a first, coarse setting of the timer, at which the actual
time delay period is observed. Additional, finer settings
can then be made until the actual time delay period is
exactly, or within a tolerable amount of, the desired
time delay period. The fewer settings that are needed,
the better i5 the measure of adjustability of the timer.
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Adjustability can be adversely affected in the
manner of backlash or hysteresis, so that a timer pro-
vides inconsistent time delays from one setting to the
next. This is observed when a timing reference mark is
moved away from a scale mark, and is then moved back
again to that mark, and where the resulting time delay
is different for the second setting than for the first.
Generally speaking, this is caused by a change in the
shape of the valve opening and the rate of air flow there-
through. More specifically, this can be caused by the
rotation of a valve needle that is not concentrically
formed around its longitudinal axis, though still within
manufacturing tolerances. The shape of the valve opening
can also be changed when the valve needle is shifted lat-
erally, or tilted to a position non-parallel to the
longitudinal axis of its surrounding chamber.
In a prior construction, a rectangular flange formed
on a valve needle to limit rotation is separated by a
narrow gap from the interior walls of the valve chamber.
This allows the needle to rotate, shift or tilt, or pos-
sibly move in all of these ways, with an adverse effect
on the adjustability of the device.
The invention is incorporated in a pneumatic timing
device with improved adjustability, the timing device
including a bellows and a body having a valve chamber
and having a passageway of substantially circular
cross section that extends along a longitudinal axis
from the valve chamber into the interior of the bellows,
the body forming a valve seat around the passageway.
A valve needle with the longitudinal axis has a
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shaft disposed for axial movement in the valve chamber
and has a non-circular cross section portion formed
around the shaft, positioned within the valve chamber
and cooperating with a non-circular cross section portion
of the body to restrict rotation of the needle, the valve
needle also forming a valve stem of substantially circu-
lar cross section that extends along the needle axis
into the passageway.
Biasing means are disposed within the valve chamber
in relative sliding contact against at least one side of
the valve needle portion that restricts rotation. The
biasing means extends the distance traveled by such
restricting portion, to urge the valve stem into contact
with a portion of the valve seat, and into a position
where the needle axis is spaced off-center from the longi-
tudinal axis so the passageway will form a crescent-shaped
bleed area.
A rotatable adjustment means is mounted on the body
and coupled to the valve needle for axial movement of
the valve needle along the biasing means, the portion of
the valve needle that restricts its rotation being in
sliding contact with the biasing means to further re-
strict rotation and to limit tilt of the valve needle,
thereby maintaining the shape and the orientation of
the bleed area.
The invention enables one to provide a pneumatic
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timer that can be easily and accurately set to provide
a desired time delay.
The invention also enables one to counteract the
effects of looseness, play and tolerance variations in
S the mechanical parts of a pneumatic timer.
With the invention one retains the ability to
easily operate the mechanical adjustment knob.
The invention also minimizes the effects of shock
and vibration upon a relay timing device used in an
industrial environment.
In drawings which illustrate the embodiments of
the invention,
Fig. 1 is a top view of a time delay relay that
includes a pneumatic timer of the present invention,
Fig. 2 is a vertical view in cross section of the
time delay relay, and the pneumatic timer included therein,
taken in the plane indicated by line 2-2 in Fig. 1,
Fig. 3 is a perspective view of the pneumatic
; timer of Figs. 1 and 2, with the cover and gear mechanism
removed to provide a view into the top of the valve
chamber,
Fig. 4 is a vertical view in cross section of
the pneumatic timer taken through the plane indicated
by line 4-4 in Fig. 2,
Fig. 5 is a perspective view of two springs seated
in the valve chamber in Fig. 3,
Fig. 6 is a top detail view of the valve chamber
seen in Fig. 3,
Fig. 7 is a view in cross section taken in the
plane indicated by line 7-7 in Fig. 4,
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Fig. ~ is a perspective view of a spring included
in a second embodiment of the invention,
Fig. 9 is a top detail view of the same area as
Fig. 6 for a second embodiment of the invention,
Fig. lO is a view in cross section in the same
plane as Fig. 7 for a second embodiment of the invention,
Fig. ll is a graph on a semilog scale of a timing
function curve for a typical pneumatic timer,
Fig. 12 is a graph on a semilog scale of a portion
of a timing function curve for a pneumatic timer of the
prior art, and
Fig. 13 is a graph on a semilog scale of a portion
of a timing function curve for a pneumatic timer of the
present invention.
A preferred embodiment of the invention is incor-
porated in a time delay relay lO seen in Figs. l and 2,
and more particularly, in a pneumatic timer ll that is
mounted on an upper housing 12 of the relay 10. A set
of four levers 13, disposed within the upper housing 12
in Fig. 2 are coupled to a movable armature of a relay
electromagnet (not shown), to reset an actuator button
14 on the pneumatic timer ll upon either the energizing or
deenergizing of the relay electromagnet. The actuator
button 14 is also coupled through two of the levers 13 to
a contact actuator (not shown) in the relay 10 to operate
a set of contacts (not shown). The contacts are housed
within cartridges having terminals 15 that extend out
from beneath a cover 16 above the contact cartridges
as seen in Fig. 1.
The actuator button 14 moves downward over different
time periods, according to the setting of the timer 11, to
actuate the contacts after a delay from the energizing
or deenergizing of the relay electromagnet. The details
of this contact actuation are set forth in Selas, U.S.
Patent No, 4,179,676, issued December 18, 1979, and
assigned to the assignee of the present invention. The
operation and the internal construction of the pneumatic
timer 11, without the improvement of the present invention,
is described in U.S. Patent No. 4,303,147, which is
assigned to the assignee of the present invention.
As seen in ~ig. 2, the pneumatic timer 11 sits upon
the upper housing 12 and closes a cavity 17 formed therein.
A collapsible bellows 18 depends from a thin, metal,
horizontal mounting plate 19 attached to the bottom of
a timer body 20. The body 20 is molded from a thermo-
plastic resinous material into a complex configuration
with a number of cavities to be described.
The body 20 has a hollow barrel 21 extending down-
ward through an opening in the mounting plate 19 into
the interior of the bellows 18. An interior surface with-
in the barrel 21 forms valve seat 22 around a verticalair passageway 23. The flow of air through this pas-
sageway 23 is controlled according to the position of
a tapered valve stem 24 to control the rate at which
the bellows 18 and the actuator button 14 advance
during a timing operation.
The air passageway 23 opens at its upper end into a
primary valve chamber 25, and a valve needle 26 extends
through the valve chamber 25 and forms the valve stem 24
that extends into the air passageway 23. A horizontal air
inlet duct 27 opens at one end into the valve chamber 25
and opens at its other end into one side of a rectangular
filter chamber 28. An air filter 29 is disposed over the
mouth of the air filter chamber 28 to filter air that is
drawn from the relay housing cavity 17, through an opening
30 in the mounting plate 19. Air is drawn from the large
cavity 17 in the upper housing 12 to the interior of the
bellows 18, to allow it to expand. Air is exhausted from
the interior of the bellows 18 back into the housing
cavity 17 as the bellows is compressed by the upward reset
stroke of one of the levers 13 against the actuator button
14.
If the upward movement of the actuator button 14
is too rapid, the bellows will not collapse quickly enough
unless some other escape is provided for the air within.
Therefore, as seen in Figs. 2 and 4, the bellows have a
raised check valve seat 31 that surrounds an opening in
the center of a reinforced bottom wall 32. A check valve
member 33 with a cup-shaped upper end is housed within
the bellows 18, and a check valve flange 34 rests upon
the check valve seat 31. A depending shaft 35 couples the
check valve flange 34 to the actuator button 14, through
the bottom wall 32 of the bellows 18, so that the actuator
button 14 and the shaft 35 move in unison. When the
bellows 18 is not collapsing as fast as the actuator
button 14 is moving upward, the check valve flange 34
moves apart from the check valve seat 31 against the force
of a spring (not shown) in the upper end of the actuator
hutton 14, to allow more air to escape and to allow the
bellows 18 to collapse more rapidly.
Still referring to Figs. 2 and 4, a bellows return
spring 36 encircles the check valve member 33, and is
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captured between the check valve flange 34 at the bottom
and an annular seat formed on the bottom of the timer
housing 20 around the barrel 21 enclosing the air passage-
way 23. This bellows return spring 27 provides a downward
S force upcn the check valve flange 34 and the bottom wall
32 of the bellows 18; however, the rate of downward move-
ment of the bellows 18 is limited by the amount of air
which can be taken into its interior. By admitting air
into the bellows 18 at a controlled rate, downward move-
ment Gf the actuator button 14 is controlled to provide atime delay.
The amount of air admitted and released through
the air passageway 23 is determined by the vertical move-
ment of the valve needle 26, seen in Figs. 2 and 4. The
valve needle 26 is raised or lowered to insert or withdraw
the valve stem 24, and to thereby regulate the size of the
bleed area between the valve stem 24 and the valve seat
22. Both the valve stem 24 and the valve seat 22 taper
the same amount from wide to narrow as they extend down-
ward. The upper end of the valve needle 26, seen best inFig. 3, is formed as a threaded shaft 36 for engagement
within a central opening of an adjustment knob 37, as seen
in Figs. l and 4. The adjustment knob 37 controls the
elevation of the valve needle 26 and the position of the
valve stem 24 relative to the valve seat 22. The valve
needle 26 also has a rectangular flange 38 between its
stem 24 and its threaded shaft 36 to prevent the needle
from rotating within the valve chamber 25.
Referring again to Fig. 2, a gear mechanism includes
a small diameter driving gear 39 that is formed as an
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integral part of the adjustment knob 37. This gear 39
meshes with a relatively larger intermediate gear 40 that
is formed together with a pinion gear 41 to provide an
idler gear member 42. The idler gear member 42 is mounted
by a boss 43 that fits in a bearing seat 44 in the body
20. The pinion gear 41 engages a large output gear 45
that encircles the adjustment knob 37 and rotates inde-
pendently of the adjustment knob 37. As explained in
U.S. Patent No. 4,303,147, cited above, these gears
are selected to provide a gear reduction between the
movement of the adjustment knob 37 and the movement of
a reference marker 46 seen in Fig. l. The reference
marker 46 is formed on a raised annular portion 47 of
the output gear 45, seen best in Fig. 2. A trans-
lS parent collar 48 fits around the adjustment knob 37 andallows the reference marker 46 to be observed as seen in
Fig. l. The transparent collar 48 is serrated around its
periphery to be more easily grasped and turned to adjust
the elevation of the valve needle 26. As seen in Fig. 2,
the gear mechanism just described is enclosed within a
body cavity 59, by a top cover plate 49 on which a scale
50 is provided as seen in Fig. 1.
In practice, the scale 50 on the top cover plate 49
provides an approximate setting for the time delay opera-
tion of the timer ll. To set the timer ll, the referencemarker 46 is aligned with a mark on the scale 50 that
represents the desired time delay. The actual timing
operation is then observed and the actual result compared
with the scale mark. The adjustment knob 37 can then be
further rotated in either direction by grasping the trans-
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parent collar ~8 and rotating it to obtain a more exactsetting.
A characteristic of mechanically adjustable devices,
such as the timer 11, is "backlash." Backlash is rneasured
by adjusting a device to a first setting to obtain a given
output, such as the advance of the actuator button 14 over
a time delay period. The adjustment knob 37 is first
rotated several turns in one direction and then rotated
back to a second setting, which provides the same output
as the first setting. Due to backlash these two settings
do not coincide as measured by the scale 50 on the cover
plate 49.
As seen best in Fig. 4, a rotational movement of the
adjustment knob 37 is translated into an axial rnovement of
the valve needle 26, to cause an advance into, or a with-
drawal from, the threaded opening in the adjustrnent kno
37. The needle flange 38 cannot completely eliminate rota-
tion because its manufacturing tolerance is such that a
small gap exists between its edges and the inside walls of
the valve chamber 25~ Therefore, absent the invention,
the valve needle 26 would be allowed to rotate a short
distance before being restricted by the interior walls of
the valve chamber 25. During this rotation, the valve
needle 26 does not move axially, but the reference marker
46 is driven through the gear mechanism. This play between
the valve needle 26 and the reference marker 46 provides
some amount of mechanical backlash or hysteresis.
In most instances, nonaxial movement of the valve
needle 26, including rotation, shifting or tilting, affects
the shape of the bleed area between the valve needle stem
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24 and the valve seat 22. The crescent-shaped bleed
area provided by the present invention is shown in Figs.
7 and 10. In the prior art it was the practice to dis-
pose the valve stem 24 concentrically in the air passage-
way 23 so that the longitudinal axes of the valve needle
26 and the air passageway 23 coincided. A truly concentric
relationship is difficult to obtain, however, because the
valve ster.l 24 and the valve seat 22 may not be perfectly
circular in cross section, and the longitudinal axis of
the valve needle 26 may be shifted or tilted slightly due
to the sum effects of tolerance variations in the adjust-
ment mechanism. In the present invention, as seen in Figs.
7 and 10, the axis of the valve needle 26 is off-center
from the axis of the air passageway 23 so that the needle
26 is eccentrically disposed in the air passageway 23.
This is accomplished by biasing the needle 26 within the
valve chamber 25.
As shown in the preferred embodiment of the invention
in Figs. 3, 4 and 6, the valve chamber 25, which is formed
in a hub 51 of the timer body 20, is enlarged on one side
to form a spring seat 52. The spring seat 52 and two
planar, biasing springs 53 disposed therein, extend the
length of the valve chamber 25 as seen in Fig. 4. The
spring seat 52 is wider than the valve chamber 25, as seen
in Figs. 3 and 6, and includes two corners 54 formed
within the hub 51 to hold opposite edges of the springs
53 slightly inward of two corners of the needle flange
38. The springs 53 are thereby held in concave position
against one side of the needle flange 38. A washer 60
slides down over the needle shaft 34 and seals the top
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of the valve chamber 25 as seen in Fig. 4O The
sprinys 53 exert a lateral force on one side of the
needle flange 38 to urge the valve needle 26 in a
lateral direction until the tapered stem 24 contacts
a portion of the valve seat 22 as seen in Figs. 4 and 7.
The springs 53 have a nominal thickness of .004
inches and are of cold rolled, carbon spring steel AlSl
1095, Rockwell Coefficient 48/51, tempered, polished
and blued. The springs 53 have a relatively high spring
rate of 1,050 pounds/inch, which is lowered slightly
from the individual spring rate with the use of two
nested springs 53, as seen in Fig. 5, instead of a
single spring. A single spring of suitable spring rate
can also be used.
In usage, the springs 53 become permanently creased
a slight amount so that the corners of the needle flange
38 track in the creases 55 seen in Fig. 5. Thus, the
springs 53 take a small amount of set which compensates
for tolerance variations to maintain a relatively constant
biasing force, even when the timer is subjected to vibra-
tions of the type encountered in an industrial environ-
ment. The valve needle 26 is also guided as the corners
of the needle flange 38 track along their respective
creases 55 iIl the springs 53.
In a second embodiment illustrated in Figs. 8-10,
a curlicue spring 53a with fluted sides is disposed in
a rectangular valve chamber 25a and bears against two
sides of the valve needle flange 38. As seen in Fig. 10,
the needle stem 24 is again urged laterally into engage-
ment with the valve seat, however, at a slightly different
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location than in the previous embodiment. In both embod-
iments, the valve stem 24 maintains its contact with the
valve seat 22 as it is inserted into and retracted from
various positions within the air passageway 23 The
curlicue spring 33a is preferably made of .005 inch nom-
inal thickness, spring-tempered stainless steel.
In both of these embodir~ents backlash and needle
rotation are minimized. The size of the bleed area and
the volume of the open part of the air passageway 23
changes as the position of the needle is adjusted, how-
ever, the shape of the bleed area remains substantially
constant.
Fig. 11 is a semilog plot of the timing function
curve 56 for a typical pneumatic timer. It shows time
delay in seconds, on a logarithmic scale, as a function
of turns of an adjustment knob, plotted on a linear
scale. Ideally, this graph should approxirnate a straight
line so that an incremental change (~ Tl) between, for
example, three turns and four turns of the adjustment
knob 37, will produce the same ratio ( ~t/t) of change
in the time delay operation as an adjustment of the knob
37 from six turns to seven turns (~ T2). For two settings
Sl and S2 of the timer in Fig. 11, it can be seen that a
decrease in the time delay to points Sl' and S2', respec-
tively, produces a ratio of change in the time delay of
the same order. This is also true for an increase in
the time delay achieved by clockwise operation of the
adjustment knob 37 to change the setting from points S
and S2 to points Sl" and S2'', respectively-
The timing curve should ideally be as smooth as
possible without alternating peaks and depressions. These
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peaks and depressions are usually observed when a
portion of a timing curve 57 is examined on an enlarged
scale as seen in Fig. 12. There the time delay does not
decrease at the same rate and, in fact, increases at
around three turns. This makes it difficult to obtain a
fine setting for the timer, because after the first,
coarse setting, a smaller adjustment of the knob may result
in a time delay that is farther from the desired value than
observed with the first setiing. Such a timing curve
results from a change of shape of the bleed area caused
by tolerance variations in the mechanical parts of the
timer.
A timing function curve 58 for a sample of a
pneumatic timer that incorporates the present invention
is seen in Fig. 13. The curve approximates a straight
line in the examined segment, and no peaks or depressions
are observed. This means that the pneumatic timer will
be more easily and more exactly set for the desired
period of time delay operation. It also means that
any tolerance variations in the mechanical parts of the
timer adjustment have been minimized or compensated for.
Although the needle flange 38 provides a convenient
point to apply biasing force, other embodiments of the
invention may apply this biasing force to other portions
of the valve needle. Therefore, the following claims
shall define the scope of the invention.
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